Date of Award

Spring 5-14-2015

Degree Type

Dissertation

Degree Name

PhD Health Sciences

Department

Health and Medical Sciences

Advisor

Lee Cabell, Ed.D

Committee Member

Richard Boergers, Ph.D.

Committee Member

Fortunato Battaglia, Ph.D.

Keywords

self-myofascial release, static stretching, GIRD

Abstract

Purpose: The purpose of this study was to examine the acute effects of a) self-myofascial release (SMR), b) static stretching (SS), and c) the combination of self-myofascial release and static stretching (SMR+SS) on glenohumeral internal rotation range of motion and markers of shoulder performance (i.e. glenohumeral external rotation isometric strength, motor unit recruitment, and throwing velocity) in male softball players with glenohumeral internal rotation deficit (GIRD).

Methods: The sample consisted of 12 male amateur softball players (age: 36.92 ±11.17 years; height: 177.42 ±6.30cm; mass: 87.58 ±18.39kg) who exhibited ≥20° less internal rotation range of motion (ROM) in the throwing shoulder compared to the non-throwing shoulder. All participants performed each of the three conditions of SMR, SS, and SMR+SS on three separate sessions. Dependent variables of glenohumeral internal rotation ROM (deg), glenohumeral external rotation isometric strength (N), motor unit recruitment using surface electromyography (EMG) of infraspinatus (agonist), pectoralis major (antagonist), and latissimus dorsi (antagonist) during isometric strength testing (% of MVC), and overhead throwing velocity (m/sec) were measured pre- and post-intervention.

Results: Glenohumeral internal rotation ROM significantly increased in all three conditions of SMR (3.84° ± 1.42; p = .0001; d = .77), SS (8.58° ± 4.42; p = .0001; d = 1.40), and SMR+SS (10.15° ± 4.95; p = .0001; d = 1.62). The conditions of SS (p = .01; d = 1.19) and SMR (p = .001; d = 1.43) improved ROM significantly more than SMR alone. SMR+SS resulted in a slightly greater increase in ROM (1.57°) when compared to SS alone, but the difference was not statistically significant. None of the three conditions resulted in decreases in glenohumeral external rotation isometric strength, motor unit recruitment, or throwing velocity. However, SMR+SS resulted in the most significant increase in infraspinatus EMG magnitudes (7.52% ± 9.23; p = .02; d = 0.82) and decrease in pectoralis major (5.90% ± 7.98; p = .03; d = 0.62) and latissimus dorsi (11.88% ± 17.28; p = .04; d = 0.80) EMG magnitudes during glenohumeral external rotation isometric strength testing.

Conclusions: According to the results, all three conditions significantly improved glenohumeral internal rotation ROM, in theory decreasing risk of injury without negatively affecting performance (i.e. isometric strength, motor unit recruitment, and throwing velocity). However, SS and SMR+SS improved ROM significantly more than SMR alone. There was no significant difference in improvements in ROM between SS and SMR+SS, Therefore, if the athlete has a limited amount of time to perform a pre-activity warm-up period (i.e. 3-4 min), it is recommended to use SS to improve ROM. However, if the athlete has more time available to warm up (i.e. 7-8 min), it is recommended to perform SMR+SS which may result in an even greater increase in ROM and possible improvements in motor unit recruitment.

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